Block copolymer, method of making the same, diamine precursors of the same, method of making such diamines and end products comprising the block copolymer

ABSTRACT

Block copolymers having a repeating unit comprised of polysiloxane and urea segments are prepared by copolymerizing certain diaminopolysiloxanes with diisocyanates. The invention also provides novel diaminopolysiloxanes useful as precursors in the preparation of the block copolymers and methods of making such diaminopolysiloxanes. Pressure sensitive adhesive compositions comprising the block copolymer are also provided as are sheet materials coated with the same.

This is a continuation-in-part of application Ser. No. 08/065,805, filedMay 21, 1993, now abandoned which is a divisional of Ser. No .07/616,753, filed Nov. 16, 1990, now U.S. Pat. No. 5,214,119, which is acontinuation of application Ser. No. 07/273,977 filed Nov. 21, 1988, nowabandoned, which is a continuation-in-part of U.S. Ser. No. 07/057,570,filed Jun. 15, 1987, now abandoned, which is a continuation-in-part ofU.S. Ser. No. 06/876,918, filed Jun. 20, 1986, now abandoned.

FIELD OF THE INVENTION

The present invention relates to organopolysiloxane-polyurea blockcopolymers, a method of making the same and certain noveldiaminopolysiloxanes useful as precursors for making the blockcopolymers. The invention also relates to methods of making the noveldiaminopolysiloxanes. In a further aspect, the invention relates toproducts which employ the block copolymer such as pressure-sensitiveadhesive compositions.

BACKGROUND OF THE INVENTION

Block copolymers have long been used to obtain desirable performancecharacteristics in various products such as films, adhesives and moldedarticles. Block copolymers are particularly useful because the blockscan be chemically tailored to optimize desired characteristics.

Siloxane polymers have unique properties derived mainly from thephysical and chemical characteristics of the siloxane bond. Suchproperties include low glass transition temperatures, high thermal andoxidative stability, UV resistance, low surface energy andhydrophobicity, good electrical properties and high permeability to manygases. They also have very good biocompatibility and are of greatinterest as biomaterials which can be utilized in the body in thepresence of blood.

Unfortunately, despite these desirable features, mostpolydimethylsiloxane polymers based solely on polydimethylsiloxane lacktensile strength. Consequently, several references suggest ways forconveniently increasing the strength of siloxane polymers especiallyelastomers. For example, various references suggest that mechanicalproperties of polysiloxane polymers can be improved substantiallythrough the preparation of block copolymers which include as a repeatingunit a "soft" polysiloxane block or segment and any of a variety ofother "hard" blocks or segments such as polyurethane. See, for example,(Ward) U.K. Pat. No. GB 2 140 444B, published Jun. 5, 1985, (Cavezzan etal) U.S. Pat. No. 4,518,758, (Nyilas) U.S. Pat. No. 3,562,352, and(Kira) U.S. Pat. No. 4,528,343.

Segmented polydimethylsiloxane polyurea elastomers, with siliconesegment molecular weights less than about 4,000, prepared from siliconediamines and diisocyanates are described in Polymer, Vol. 25, pages1800-1816, December, 1984.

However, elastomers with silicone segment molecular weights greater thanabout 4,000 have not been described in the literature. This reflects thedifficulty of obtaining silicone diamines of sufficient purity havingmolecular weights greater than about 4,000. Inherent in the conventionalmethod of preparation of silicone diamines is the generation ofmonofunctional and nonfunctional impurities in the desired diamineproduct. These contaminants have the same average molecular weight asthe diamine but cannot be removed from the diamine. Thus, elastomersobtained by chain extension of these silicones contain these impurities,and the elastomeric properties are negatively affected by them. Forexample, monofunctional impurities inhibit the chain extension reactionand limit the attainment of optimum molecular weight, and therebyoptimum tensile strength, of the polyurea. Nonfunctional silicone oilcan act as a plasticizing agent, which also contributes to reduction intensile strength, and such oil can bloom to the surface of the elastomerand be transferred, e.g., to a pressure sensitive adhesive in contactwith it, resulting in loss of adhesive properties.

SUMMARY OF THE INVENTION

The present invention provides organopolysiloxane-polyurea blockcopolymers having the conventional excellent physical propertiesassociated with polysiloxanes of low glass transition temperature, highthermal and oxidative stability, UV resistance, low surface energy andhydrophobicity, good electrical properties and high permeability to manygases, and the additional desirable property of having excellentmechanical and elastomeric properties. The organopolysiloxane-polyureablock copolymers of the present invention are thought to have goodbiocompatibility and are capable of being utilized in situations whereconventional polysiloxane polymeric materials have found use. Theorganopolysiloxane-polyurea block copolymers of the present inventionare particularly useful, when tackified with a compatible tackifierresin, as pressure sensitive adhesive compositions.

The organosiloxane-polyurethane block copolymers of the presentinvention are segmented copolymers of the (AB)n type which are obtainedthrough a condensation polymerization of a difunctionalorganopolysiloxane amine (which produces soft segment) with adiisocyanate (which produces a hard segment) and may include adifunctional chain extender such as a difunctional amine or alcohol, ora mixture thereof.

More specifically, the present invention providesorganopolysiloxane-polyurea block copolymers comprising a repeating unitrepresented by Formula I, as follows, the organopolysiloxane-polyureablock copolymer comprising the following repeating unit: ##STR1## where:Z is a divalent radical selected from the group consisting of phenylene,alkylene, aralkylene and cycloalkylene;

Y is selected from the group consisting of alkylene radicals of 1 to 10carbon atoms, aralkyl radicals, and aryl radicals;

R is at least 50% methyl with the balance of the 100% of all R radicalsbeing selected from the group consisting of a monovalent alkyl radicalhaving from 2 to 12 carbon atoms, a substituted alkyl radical havingfrom 2 to 12 carbon atoms, a vinyl radical, a phenyl radical, and asubstituted phenyl radical;

D is selected from the group consisting of hydrogen, an alkyl radical of1 to 10 carbon atoms, and phenyl;

B is selected from the group consisting of alkylene, aralkylene,cycloalkylene, phenylene, polyethylene oxide, polypropylene oxide,polytetramethylene oxide, polyethylene adipate, polycaprolactone,polybutadiene, and mixtures thereof, and a radical completing a ringstructure including A to form a heterocycle;

A is selected from the group consisting of ##STR2## where G is selectedfrom the group consisting of hydrogen, an alkyl radical of 1 to 10carbon atoms, phenyl, and a radical which completes a ring structureincluding B to form a heterocycle;

n is a number which is 70 or larger; and

m is a number which can be zero to about 25.

In the preferred block copolymer, Z is selected from the groupconsisting of hexamethylene, methylene bis-(phenylene), isophorone,tetramethylene, cyclohexylene, and methylene dicyclohexylene and R ismethyl.

A method of making the organopolysiloxane-polyurea block copolymer isalso provided. The method comprises polymerizing under reactiveconditions and in an inert atmosphere:

(1) a diamine having a molecular weight of at least 5,000 and amolecular structure represented by Formula II, as follows: ##STR3##where R, Y, D and n are as defined in Formula I above; (2) at least onediisocyanate having a molecular structure represented by Formula III, asfollows:

    OCN--Z--NCO                                                III

where Z is as defined in Formula I above; and

(3) up to 95 weight percent diamine or dihydroxy chain extender having amolecular structure represented by Formula IV, as follows:

    H--A--B--A--H                                              IV

where A and B are defined above.

The combined molar ratio of silicone diamine, diamine and/or dihydroxychain extender to diisocyanate in the reaction is that suitable for theformation of a block copolymer with desired properties. Preferably theratio is maintained in the range of about 1:0.95 to 1:1.05.

The diisocyanate useful in the reaction can be a phenylene diisocyanatesuch as toluene diisocyanate or p-phenylene diisocyanate, hexamethylenediisocyanate, aralkylene diisocyanate such as methylenebis-(phenyloisocyanate) or tetramethylxylene diisocyanate, or acycloalkylene diisocyanate such as isophorone diisocyanate, methylenebis(cyclohexyl)diisocyanate, or cyclohexyl diisocyanate.

The reaction to make the novel block copolymer involves the use of thenovel organopolysiloxane diamine represented by Formula II.

A method of making the organopolysiloxane diamine represented by FormulaII is also provided. The method involves:

(1) combining under reaction conditions and in an inert atmosphere:

(a) amine functional endblocker of the molecular structure representedby Formula V, as follows: ##STR4## where D and Y are as defined inFormula I, and each R is independently selected from the groupconsisting of a monovalent alkyl radical having from about 1 to about 12carbon atoms, a substituted alkyl radical having from about 1 to about12 carbon atoms, a phenyl radical and a substituted phenyl radical;

(b) sufficient cyclic siloxane to react with said amine functionalendblocker to form a lower molecular weight organopolysiloxane diaminehaving a molecular weight less than about 2,000 and a molecularstructure represented by Formula VI, as follows: ##STR5## where D, R,and Y are as defined in Formula I, and x is a number in the range ofabout 4 to 40;

(c) a catalytic amount not to exceed about 0.1% by weight based on theultimate weight of the final organopolysiloxane diamine of a novelessentially anhydrous amine silanolate catalyst of a molecular structurerepresented by Formula VII, as follows ##STR6## where D and Y are asdefined in Formula I and each R is independently selected from the groupconsisting of a monovalent alkyl radical having from about 1 to about 12carbon atoms, a substituted alkyl radical having from about to about 12carbon atoms, a phenyl radical and a substituted phenyl radical, and M⁺is a cation selected from the group consisting of K⁺, Na⁺, or N(CH₃)₄ ⁺,with N(CH₃)₄ ⁺ being preferred;

(2) continuing the reaction until substantially all of the aminefunctional endblocker is consumed; and

(3) adding additional cyclic siloxane until the novel organopolysiloxanediamine represented by Formula II is obtained.

The preferred amine silanolate catalyst is 3-amino-propyl dimethyltetramethylammonium silanolate. The catalytic amount of the aminesilanolate catalyst is preferably less than 0.5 weight percent, mostpreferably 0.005 to about 0.03 weight percent, based upon the ultimateweight of the final organopolysiloxane.

The preferred reaction conditions comprise a reaction temperature rangeof about 80° C. to about 90° C., a reaction time of about 5 to 7 hours,and the dropwise addition of the additional cyclic siloxane.

Also provided is a method of making an organopolysiloxane diamine havinga molecular weight of at least 2000 and having less than or equal toabout 0.010 weight % silanol impurities, and being prepared by the stepsof

(1) combining under reaction conditions:

(a) amine functional endblocker of the general formula ##STR7## where: Yis selected from the group consisting of an alkylene radical of 1 to 10carbon atoms, aralkyl, and aryl radicals; D is selected from the groupconsisting of hydrogen, an alkyl radical of 1 to 10 carbon atoms, andphenyl; and R is each independently selected from the group consistingof a monovalent alkyl radical having from 1 to 12 carbon atoms, asubstituted alkyl radical having from 1 to 12 carbon atoms, a phenylradical, and a substituted phenyl radical;

(b) sufficient cyclic siloxane to react with said amine functionalendblocker to form an intermediate organopolysiloxane diamine having amolecular weight less than about 2,000 and general formula ##STR8##where: Y and D are as defined above; R is at least 50% methyl with thebalance of the 100% of all R radicals being selected from the groupconsisting of a monovalent alkyl radical having from 2 to 12 carbonatoms, a substituted alkyl radical having from 1 to 12 carbon atoms, avinyl radical, a phenyl radical and a substituted phenyl radical; and xis a number in the range of about 4 to about 40; and

(c) a catalytic amount of a compound characterized by having a molecularstructure represented by the formula: ##STR9## where: Y and D are asdefined above; R is each independently selected from the groupconsisting of a monovalent alkyl radical having from 1 to 12 carbonatoms, a substituted alkyl radical having from 2 to 12 carbon atoms, aphenyl radical, and a substituted phenyl radical; and Q ⁺ is selectedfrom the cations Cs⁺ and Rb⁺ ;

(2) continuing the reaction until substantially all of said aminefunctional endblocker is consumed;

(3) adding additional cyclic siloxane in an amount required to obtainthe organopolysiloxane diamine of the desired molecular weight;

(4) terminating the reaction by addition of a volatile organic acid toform the organopolysiloxane diamine of at least about 2000 molecularweight having less than or equal to about 0.010 weight percent silanolimpurities; and

(5) removing any residual cyclic siloxanes and volatile impurities.

Preferred amine silanolate compounds of Formula VIII are cesium3-aminopropyldimethyl silanolate and rubidium 3-aminopropyldimethylsilanolate. The catalytic amount of the amine silanolate catalyst ispreferably less than 0.025 weight percent, most preferably 0.0025 toabout 0.01 weight percent, based upon the ultimate weight of the finalorganopolysiloxane diamine. Preferred volatile organic acids areselected from the group consisting of acetic acid, trimethylacetic acid,trichloroacetic acid, trifluoroacetic acid, benzoic acid, and mixturesthereof. The preferred reaction conditions comprise a reactiontemperature range of about 150° C. to about 160° C. and a reaction timeof about 4 to 8 hours.

The present invention also relates to a method of making anorganopolysiloxane diamine having a molecular weight greater than about2000 and having less than or equal to about 0.010 weight % silanolimpurities, comprising the steps of:

(a) combining under reaction conditions

(i) an amine functional endblocker represented by the formula IX##STR10## wherein; Y is selected from the group consisting of alkyleneradicals comprising about 1 to about 10 carbon atoms, aralkyl radicals,and aryl radicals;

D is selected from the group consisting of hydrogen, an alkyl radical ofabout 1 to about 10 carbon atoms, and phenyl;

R is at least 50% methyl with the balance of the 100% of all R radicalsbeing selected from the group consisting of a monovalent alkyl radicalhaving 2 to 12 carbon atoms, substituted alkyl radical having from 2 to12 carbon atoms, a vinyl radical, a phenyl radical, and a substitutedphenyl radical; and

x represents an integer of about 1 to about 150;

(ii) sufficient cyclic siloxane to obtain said organopolysiloxanediamine having a molecular weight greater than about 2000;

(iii) a catalytic amount of a compound selected from the groupconsisting of cesium hydroxide, rubidium hydroxide, cesium silanolates,rubidium silanolates, cesium polysiloxanolates, rubidiumpolysiloxanolates, and mixtures thereof;

(b) continuing the reaction until substantially all of said aminefunctional endblocker is consumed;

(c) terminating the reaction by the addition of a volatile organic acidto form a mixture of an organopolysiloxane diamine having greater thanabout 0.010 weight % silanol impurities and one or more of thefollowing: a cesium salt of the organic acid, a rubidium salt of theorganic acid, both a cesium salt of the organic acid and a rubidium saltof the organic acid; wherein a molar excess of organic acid is added inrelation to the compound of element (a)(iii);

(d) condensing under reaction conditions a sufficient amount of saidsilanol impurities to form an organopolysiloxane diamine having lessthan or equal to about 0.010 weight % silanol impurities; and

(e) optionally removing said salt.

DETAILED DESCRIPTION OF THE INVENTION

The reaction to produce the block copolymer of the invention involvesmixing under reactive conditions the organopolysiloxane diamine, diamineand/or dihydroxy chain extender, if used, and diisocyanate to producethe block copolymer with hard and soft segments respectively derivedfrom the diisocyanate and organopolysiloxane diamine. The reaction istypically carried out in a reaction solvent.

Preferred reaction solvents are those which are unreactive with thediisocyanates and which maintain the reactants and products completelyin solution throughout the polymerization reaction. It has been foundthat chlorinated solvents, ethers, and alcohols perform best in the caseof aliphatic diisocyanates with methylene chloride, tetrahydrofuran, andisopropyl alcohol being preferred. For aromatic diisocyanates such as4,4'-methylene-bis-phenyl-isocyanate (MDI), a mixture of tetrahydrofuranwith 10% to 25% by weight of dipolar aprotic solvent such asdimethyl-formamide is preferred.

The starting materials and reaction solvents are usually initiallypurified and dried and the reaction is carried out, under an inertatmosphere such as dry nitrogen or argon.

Suitable diisocyanates include toluene diisocyanate and hexamethylenediisocyanate. Preferred diisocyanates include4,4'-methylene-bis-phenylisocyanate (MDI),4,4'-methylene-bis(cyclohexyl)diisocyanate (H-MDI) and isophoronediisocyanate.

Chain extenders may be incorporated with the other reactants to provideother physical properties in the claimed block copolymer. The chainextenders may be short chain diamines such as hexamethylene diamine,xylylene diamine, 1,3-di(4-piperidyl)propane (DIPIP), N-2-aminoethylpropylmethyldimethoxysilane (DAS), piperazine and the like, withpiperidyl propane being preferred.

Polymeric diamines as well as polymeric glycols may also becopolymerized with the polysiloxane diamines, diisocyanates, and otheroptional non-silicone soft segments as chain extenders to impartadditional desirable properties to the silicone polyureas. The resultantcopolymeric segments may comprise from as little as 5% to as much as 95%of the copolymer formulation, depending on the properties of theresultant copolymer desired.

Polymeric diamines useful as nonsilicone soft segments are those whichcan be obtained with functionality approaching 2.0 such aspolytetramethylene oxide diamine of from 5,000 to 25,000 molecularweight, with a molecular weight in the range of 8,000 to 15,000 beingmost preferred. Suitable polymeric diols include polytetramethyleneoxide glycol, polyethylene oxide glycol, polyethylene adipate glycol,polypropylene oxide glycol, polybutadiene glycol, polycaprolactoneglycol, and the like. In preparing the polyureas from a mixture ofpolysiloxane and polytetramethylene oxide diamines, the diamines aredissolved together in a suitable solvent such as methylene chloride andthe diisocyanate and chain extender, if used, are introduced into themixture, preferably at a combined amine to diisocyanate molar ratio of1:0.95 to 1.05. A two stage procedure is required to copolymerize thepolymeric glycols with silicone diamines in which the glycol is firstheated with the diisocyanate in an inert solvent such as toluene ortetrahydrofuran with a catalytic amount of a tin compound such asstannous octoate or dibutyl tin dilaurate for a sufficient amount oftime, e.g., one half to one hour, until all of the alcohol groups havebeen capped with isocyanate. In the second stage, the polysiloxanediamine is added followed by any optional diamine chain extenders toprovide the polyether or polyester polyurethane polysiloxane polyureablock copolymer, with the combined molar ratio of amine plus alcohol toisocyanate preferably being held in the range of 1:0.95 to 1:1.05 toprovide for complete reaction.

The organopolysiloxane-polyurea block copolymers of this invention,useful as films or coatings, are prepared in and cast from solvents.

A significant feature of the invention is the discovery thatsubstantially pure organopolysiloxane diamines can be produced with apreselected desired molecular weight in excess of 5,000 with excellentdifunctionality. It is thought such organopolysiloxane diamines areproduced according to the present invention with such high puritybecause of the presence of the following key process conditions duringthe preparation:

1. utilize an anhydrous amino alkyl functional silanolate catalyst suchas tetramethylammonium 3-aminopropyldimethyl silanolate;

2. use a minimum amount of this catalyst, preferably less than 0.05% byweight based upon the weight of the silicone diamine being prepared; and

3. run the reaction in two stages, as herein described.

As previously mentioned, the reaction to produce the organopolysiloxanediamine employs an anhydrous amine functional silanolate catalystrepresented by Formula VII. The preferred catalyst in thispolymerization is 3-amino-propyl dimethyl tetramethylammoniumsilanolate, itself a novel compound, obtained as a crystalline solidfrom the reaction of one molar equivalent of 1,3bis-(3-aminopropyl)tetramethyldisiloxane with 2 molar equivalents oftetramethylammonium hydroxide pentahydrate in tetrahydrofuran underreflux, followed by drying under vacuum for 5 hours (0.1 mm) at 60° C.

In the first stage of the reaction, a low molecular weight siliconediamine having a structure as defined by Formula VI is prepared byreacting an amine functional disiloxane endblocker of the typerepresented by Formula V with a cyclic siloxane in the presence of acatalytic amount of anhydrous amine functional silanolate represented byFormula VII in an inert atmosphere such as nitrogen or argon. The amountof catalyst employed should be less than 0.05 weight percent, preferably0.005 to about 0.03 weight percent, by weight of the resultant diaminosilicone. While not wanting to be bound by theory, it is thought that,by using a minimum amount of an anhydrous amine functional silanolatecatalyst, the number of inactive chain ends that are produced bycatalyst molecules and spurious water are held to a minimum.

The reaction is typically carried out in bulk at a temperature of80°-90° C., and under these conditions is usually complete in about0.5-2 hours, as judged by substantially complete disappearance of theendblocker of the reaction mixture as determined by vapor phasechromatography. An intermediate organopolysiloxane diamine is obtainedhaving a molecular weight of less than about 2,000 and a molecularstructure represented by Formula VI.

The second stage of the reaction involves the slow addition of theremainder of the cyclic siloxane required to achieve the desiredmolecular weight, preferably dropwise addition, at such a rate that thecyclic siloxane is incorporated into the polymer about as fast as it isadded, usually in about 5 to 7 hours at the reaction temperature of80°-90° C. The desired organopolysiloxane diamine is produced having amolecular weight in excess of 5,000 and a structure as defined byFormula II. By utilizing this two-stage method with a minimum amount ofamine functional anhydrous silanolate catalyst, silicone diamines ofFormula II may be consistently prepared in any desired molecular weightfrom about 5,000 to about 70,000 having excellent difunctionality withlittle contamination from monofunctional and nonfunctional polysiloxaneimpurities.

Substantially pure, difunctional organopolysiloxane diamines of FormulaII wherein "n" is 30 or greater, having a molecular weight of greaterthan about 2,000, preferably greater than about 5,000, may also beprepared using an alternative, yet related, two stage method. Thismethod consists of combining the amine functional disiloxane endblockerof the type represented by Formula V with a cyclic siloxane in an inertatmosphere such as nitrogen or argon. These reagents are then heated andpurged with inert gas to dispel water vapor and the volatilecontaminants, such as carbon dioxide, which effectively poison thesilanolate polymerization catalyst. After heating to about 150° to about160° C., a solution of the anhydrous cesium or rubidium silanolatecatalyst (as described in Formula VIII) in toluene is added. The amountof catalyst employed should be less than about 0.025% by weight,preferably from about 0.0025 to about 0.01% based on the weight oforganopolysiloxane diamine products. As discussed supra, it is thoughtthat the use of minimum amount of an anhydrous amine functionalsilanolate catalyst provides a means to reduce the level of undesiredmonofunctional and nonfunctional polysiloxane impurities in the finalorganopolysiloxane diamine product.

The reaction is typically carried out in bulk at a temperature of about150° to about 160° C., and under these conditions is usually complete inabout 0.5 to about 2.0 hours, as judged by substantially completedisappearance of the endblocker of the reaction mixture as determined byvapor phase chromatography. An intermediate organopolysiloxane diamineis obtained having a molecular weight of less than about 2,000 and amolecular structure represented by Formula VI.

The next step of the reaction involves the addition of the remainder ofthe cyclic siloxane monomer required to achieve the desired molecularweight. When the added cyclic siloxane has been totally consumed,usually in about one to two hours as judged by vapor phasechromatography, the final step of this method involves the addition ofan excess of an organic acid in an amount sufficient to neutralize thecatalyst and terminate the reaction. Such organic acids must be volatile(i.e. have a boiling point of less than about 100° C. at 1 mmHg) so thatexcess acid may be readily removed with other volatile impurities in asubsequent step of this method which involves heating the mixture undervacuum. Furthermore, the volatile organic acid must not cause there-equilibration of the reaction product which would result in thereformation of the starting materials. Examples of useful volatileorganic acids include but are not limited to those selected from thegroup consisting of acetic acid, trimethylacetic acid, trichloroaceticacid, trifluoroacetic acid, benzoic acid, and mixtures thereof. Inaddition to small amounts of free silanol, this process generates thecesium or rubidium salt of the volatile organic acid or acids employedin terminating the polymerization. These acid salts are insoluble in thesilicone diamine product at ambient temperatures, and are removed byconventional methods after the residual cyclic siloxanes and volatileimpurities have been distilled off under high vacuum at 150° to 160° C.over a period of about two to three hours.

Significantly, with prolonged heating (i.e., 4 to 10 hours at elevatedtemperatures), the cesium and rubidium salts have been found to serve aseffective catalysts for the condensation of the remaining silanolimpurities (i.e., terminal silanol, or-SiOH moieties, such asorganopolysiloxanes having 1 terminal silanol group and 1 terminal aminegroup and organopolysiloxanes having 2 terminal silanol groups) toSi--O--Si linkages, thus converting most monoamine and nonaminefunctional impurities into organopolysiloxane diamines. With thisdiscovery, it is also possible to prepare high purity, high molecularweight organopolysiloxane diamines without the necessity of utilizingminimum amounts of anhydrous amine functional silanolate catalysts.Catalytic compounds selected from the group consisting of cesiumhydroxide (which may be in aqueous solution), rubidium hydroxide (whichmay be in aqueous solution), cesium polysiloxanolates, rubidiumpolysiloxanolates, and mixtures thereof, although initially generatinghigh levels of silanol end groups, ultimately provide organopolysiloxanediamines of equivalent purity to products obtained from the anhydrouscatalyst through the condensation of terminal silanols. By utilizingthis method with a cesium-based or rubidium-based catalyst,organopolysiloxane diamines of Formula II wherein "n" may be furtherdefined as 30 or greater may be consistently and conveniently preparedin any desired molecular weight from 2,000 or more, typically about5,000 to about 250,000 or more, having excellent difunctionality withlittle contamination from monofunctional and nonfunctional polysiloxaneimpurities.

This method, which is especially useful for preparing organopolysiloxanediamines of Formula II having very high molecular weight (i.e., greaterthan 70,000) and high purity, comprises the use of a silicone diamineendblocker represented by Formula IX. In contrast to the other methodsof the present invention which employ monomeric amine functionaldisiloxane endblockers, this amine functional endblocker may furthercomprise oligomeric and polymeric silicone diamines having a molecularweight of up to 10,000 and having any level of silanol content as astarting material. Following the removal of volatile contaminants suchas water or carbon dioxide from these materials, a mixture of the aminefunctional endblocker and cyclic siloxane is heated to a temperature ofabout 100 to about 160° C., preferably to about 150° to about 160° C.,in an inert atmosphere such as nitrogen or argon. The amount of cyclicsiloxane starting material required depends both upon the molecularweight of the amine functional endblocker and the desired molecularweight of the organopolysiloxane diamine product. To this heated mixtureis then added a catalytic amount of a solution of a compound selectedfrom the group consisting cesium hydroxide, rubidium hydroxide, cesiumsilanolates, rubidium silanolates, cesium polysiloxanolates, rubidiumpolysiloxanolates, and mixtures thereof. This catalytic amount dependsupon the reactivity, availability and expense of the compound utilized.Examples of useful amounts of compounds selected from the groupconsisting of cesium hydroxide, rubidium hydroxide, and mixtures thereofrange from about 0.005 to about 1 weight percent based upon the totalweight of the endblocker and cyclic siloxane. The more highly reactiveand less common compounds selected from the group consisting of cesiumsilanolates, rubidium silanolates, and mixtures thereof may be used at alower concentration, typically from about 0.005 to about 0.3 weightpercent based upon the total weight of the endblocker and cyclicsiloxane. This reaction is then continued until completion (about 0.5 toabout 2 hours) when the expected proportion of the mixed cyclic siloxanecoproduct of this reaction is obtained (approximately 10 to 15% byweight) as determined by vapor phase chromatography.

After this level of mixed cyclic siloxane material is reached, then thereaction mixture is cooled and a sufficient amount of a volatile organicacid such as those described above is added to provide a solution ofneutral or acidic pH. Generally, the temperature must be cooled belowthe boiling point of the organic acid, preferably to temperature ofabout 60° to about 80° C. Addition of such organic acids terminates thereaction and causes the formation of the organopolysiloxane diamineproduct of the desired molecular weight, but also includes a high levelof silanol containing, monoamine and nonamine functional polysiloxaneimpurities and a small quantity of residual mixed cyclic siloxanebyproducts. An additional product of this step is the cesium and/orrubidium salt formed by the reaction of the catalyst and the organicacid used in the termination of the reaction.

This mixture of impure organopolysiloxane diamine and cesium and/orrubidium salt is then heated to about 130° to about 160° C. for a periodof about 4 to 8 hours under vacuum conditions. As described above, atelevated temperatures the cesium and/or rubidium salts present in thismixture act to catalyze the condensation reaction of substantially allsilanol impurities (to provide a product having less than 0.010 wt %silanol impurities). The vacuum is necessary to encourage this reactionas the vacuum continuously removes the water produced as a result of thecondensation of the silanol groups to form Si--O--Si linkages and theformation of substantially pure, difunctional organopolysiloxanediamines of the present invention. The vacuum also provides a means toremove the residual mixed cyclic siloxane fraction from the product. Asan optional final step, the remaining insoluble cesium and/or rubidiumsalt may be removed from the organopolysiloxane diamine by anyconventional method, such as filtration or centrifugation.

The prior art method for the preparation of amine terminated siliconesfrom the equilibration of cyclic siloxanes, amine functional disiloxanesand basic catalysts such as tetramethyl ammonium hydroxide orsiloxanolate has proven unsatisfactory for obtaining diaminoorganopolysiloxanes of molecular weight in excess of 4,000 with gooddifunctionality. These poor results are thought to be caused by a numberof deleterious factors inherent in the previous methods, which includerunning the reaction in a single stage or all at once with the catalyst,amine functional endblocker and all the cyclic siloxane together. Thisresults in incomplete incorporation of endblocker and higher thancalculated molecular weights. The use of an excessive amount of anonfunctional hydrated catalyst produces a significant percentage ofnon-amine terminated silicone polymers as impurities in the finalproduct. These results are obviated in the method of the presentinvention by the use of an essentially anhydrous amine functionalcatalyst at a minimum concentration in a two-stage reaction as describedabove.

The segmented polysiloxane block copolymers of this invention can beprepared in a wide range of useful properties through variations in theratio of soft segments to hard segment, the nature of the chainextenders and other polymers employed, and the molecular weight of thepolysiloxane segment. For example, the combination of relatively lowmolecular weight (4,000-7,000), silicone segments with relatively highhard segment content provides stiff, hard, yet flexible rubbers

It has been discovered that these copolymers are suitable for use asrelease coatings for a variety of pressure-sensitive adhesives. Theyhave a high degree of difunctionality with little contamination frommonofunctional or nonfunctional siloxane impurities, virtuallyeliminating re-adhesion problems They have good stability in solution,are film-forming, and have unusually high strength plus desirablemechanical and elastomeric properties. In addition, they do not requirehigh temperature curing or long processing times, a decided advantage inpressure-sensitive tape manufacturing.

The block copolymers of this invention, for most applications, do notrequire curing to achieve their desirable properties, but yield toughfilms upon drying. Where additional stability, solvent resistance orother additional strength is desired, the silicone block copolymers canbe crosslinked after casting or coating by any of the conventionalmethods described in the art, such as electron beam radiation, or use ofperoxides.

As mentioned previously, the segmented copolymers of this invention maybe prepared with a wide range of useful properties through variations inthe ratio of soft segments to hard segments, the amount and nature ofthe chain extenders employed, and the molecular weight of thepolysiloxane segment These variations give rise to varying amounts ofrelease, i.e., from 10 g/cm or less, to about 350 g/cm. Certaincopolymers are especially useful as low-adhesion backsizes (LABs) forremovable pressure-sensitive adhesives such as masking tapes. LABs fortapes in roll form ideally exhibit release toward the adhesive of about60 to 350 g/cm width. The preferred hard segment content for copolymersused as release agents and LABs is from about 15% to about 70%.Preferred ranges vary, depending on the type of adhesive and itsultimate use, i.e., the preferred range for LABs used in masking tapesis from about 25% to about 60%. Copolymers having this range exhibit thenecessary combination of adequate unwind on fresh tape and moderateunwind after adverse aging conditions of heat and humidity, plusacceptable paint masking performance, paint flaking resistance and theability to hold when used in overtaping applications.

Block copolymers of medium molecular weight silicone segments(7,000-25,000) alone, or combined with other elastomeric blocks and ahard segment content in the 15-25% range, provide highly elastic,resilient, quite strong silicone elastomers. With the highdifunctionality of the silicone diamines of this invention, it ispossible to prepare silicone elastomers even with very high molecularweight silicone segments (25,000-70,000) and hard segment content as lowas 0.5 to 10%. Such polymers are extremely soft and deformable andnaturally of low tensile strength; however, it has been discovered thatwhen these silicone polyureas are blended with an approximately equalweight of hydroxy-functional silicone tackifier resins commerciallyavailable as the MQ series, such as "MQ" SR-545 from the GeneralElectric Company, a new type of silicone pressure-sensitive adhesive isobtained. Through variation in silicone molecular weight and hardsegment content, pressure-sensitive adhesive can be formulated with anoptimum balance of tack, peel adhesion, and shear holding propertieswithout the necessity of post-curing reactions. Furthermore, since thecohesive strength of these polymers is a result of physical forces ofattraction between urea groups and not chemical cross-linking, thesesilicone polyurea pressure-sensitive adhesives can be coated onto tapesby hot melt extrusion processes.

This invention is further illustrated by the following examples whichare not intended to be limiting in scope. Unless indicated otherwise,the molecular weights refer to number average molecular weights.

EXAMPLE 1

Preparation of the Catalyst

A 100 ml three-necked round bottom flask equipped with magnetic stirrer,argon inlet and condenser fitted with a drying tube was charged with12.4 g (0.05 mole) of 1,3-bis (3-aminopropyl)tetramethyldisiloxane, 18.1g tetramethylammonium hydroxide pentahydrate and 30 ml oftetrahydrofuran. The mixture was stirred and heated under reflux in anargon atmosphere for 1.5 hours until a vapor phase chromatograph (VPC)showed complete disappearance of the disiloxane peak. Upon cooling, themixture separated into two layers. The tetrahydrofuran was allowed todistill from the mixture until a pot temperature of 75° C. was achieved,leaving a yellow oil which was stirred and heated under vacuum (0.1 mm)in an oil bath at 60° C. until no more volatiles distilled (ca 5 hours).The crude product, a yellow waxy solid, was recrystallized fromtetrahydrofuran (THF) under argon, filtered and dried under vacuum togive 3-aminopropyl dimethyl tetramethylammonium silanolate as a whitecrystalline solid. The chemical structure was confirmed by nuclearmagnetic resonance analysis (NMR), and the product was stored at roomtemperature under argon.

EXAMPLE 2

Preparation of Silicone Diamine

A 500 ml three-necked round bottom flask equipped with thermometer,mechanical stirrer, dropping funnel and dry argon inlet was charged with3.72 g bis (3-aminopropyl)tetramethyldisiloxane and 18 g ofoctamethylcyclotetra-siloxane (D₄) which had been previously purged for10 minutes with argon. The flask contents were heated to 80° C. with anoil bath and a trace (about 0.03 to 0.05 g) of the catalyst described inExample 1 was added via a spatula. The reaction was stirred at 80° C.and after 30 minutes of stirring had become quite viscous. VPC showedthat the endblocker had completely disappeared. To the resultantreaction mixture (which consisted of a 1,500 molecular weight siliconediamine, cyclic siloxanes and active catalyst) was added dropwise over asix hour period 330 g of argon-purged D₄, resulting in a further rise inthe viscosity. Heating the reaction flask contents at 80° C. wascontinued overnight. The catalyst was decomposed by heating at 150° C.for 1/2 hour and the product was stripped at 140° at 0.1 mm pressureuntil no more volatiles distilled (ca. 1.5 hr.), resulting in 310 g of aclear, colorless viscous oil (a yield of 88% of theoretical). Themolecular weight of the product determined by acid titration was 21,200.

Using this procedure, but varying the ratio of endblocker to D₄,silicone diamines with molecular weights from 4,000 to as high as 70,000were prepared.

EXAMPLE 3

Preparation of Silicone Polyurea

Under argon, to a solution of 10.92 g of the 21,200 MW silicone diaminedescribed in Example 2 in 65 ml of methylene chloride was added, all atonce, a solution of 0.80 g of isophorone diisocyanate (IPDI) in 15 ml ofdichloromethane, resulting in a clear solution. To the clear solutionwas added dropwise a solution of 0.65 g 1,3-dipiperidyl propane (DIPIP)in 10 ml dichloromethane. Toward the end of the addition, the viscosityrose substantially until the magnetic stirrer almost stopped, producinga clear solution of silicone polyurea with a molar ratio of siliconediamine/DIPIP/IPDI of 1:6:7. This solution was cast onto a glass plateand the solvent allowed to evaporate overnight, resulting in a clearfilm which was quite strong and highly elastic, and had a tensilestrength of 5,210 kPa, 300% elongation, and a permanent set of 5%.

The tensile strength, elongation and permanent set values were allmeasured at break. The tensile strength, percent elongation, and percentpermanent set of the elastomeric materials were determined according toASTM D 412-68 under ambient conditions at a temperature of about 23° C.According to this procedure, elastomer specimens, cast from solvent,were dried, cut to form "dumbbell"-shaped configurations, and thedumbbells were stretched to the breaking point. The stretching wasaccomplished by use of a tensile testing device which recorded thetensile strength during stretching until the test specimen broke. Thetensile strength at break in kPa was recorded. The device also recordedthe percent elongation at break to the nearest 10 percent. The percentpermanent set was determined by carefully fitting together the brokenpieces of the test dumbbell 10 minutes after the specimen had broken,measuring the combined length of the broken and stretched specimenpieces, dividing this measured length by the original length of thespecimen before stretching, and multiplying the quotient by 100.

EXAMPLES 4-15

Preparation of Silicone Polyurea

Under argon, to a solution of 2.06 g isophorone diisocyanate (IDPI) in30 ml dichloromethane was added a solution of 0.87 g 1,3-dipiperidylpropane (DIPIP) in 20 ml dichloromethane. A solution of 9.8 g ofsilicone diamine of 9,584 molecular weight in 20 ml dichloromethane wasthen added dropwise. To the resulting clear solution was added dropwisea solution of 0.86 g of DIPIP in 10 ml of dichloromethane. Toward theend of the addition, the reaction mixture became very viscous. After 1/2hour, the resultant viscous solution was cast onto a glass plate and thesolvent allowed to evaporate, producing an elastomer film of siliconepolyurea with a diamine/DIPIP/IPDI molar ratio of 1:8:9, which wasclear, yet stiff with a tensile strength of 8,453 kPa, 200% elongationand 15% permanent set.

Silicone polyureas with a wide range of elastomeric properties wereprepared by procedures illustrated in the examples above. The propertiesof a number of these silicone elastomers are listed in Table I below asExamples 5-15.

                                      TABLE I    __________________________________________________________________________    Silicone Polyurea Elastomers    Silicone            Chain Inherent    Silicone-Polyurea                                         Perm.    Ex.       Diamine            Extender                  Diisocyanate                         Inherent                              Tensile                                  Elongation at                                         Set    No.       (MW) (Moles)                  (Moles)                         Viscosity                              (kPa)                                  Break (%)                                         (%)    __________________________________________________________________________    5  5800 DIPIP (1)                  H-MDI (2)                         1.34 8280                                  600    --    6  6100 (0)   H-MDI (1)                         0.75 4623                                  750    15    7  6100 DIPIP (1)                  H-mDI (2)                         0.87 6,038                                  470    2    8  8400 DIPIP (5)                  H-MDI (6)                         0.75 7590                                  150    --    9  8400 DIPIP (8)                  IPDI (9)                         --   11247                                  260    --    10 9600 DIPIP (3)                  H-MDI (4)                         0.94 7038                                  375    15    11 9600 DIPIP (8)                  H-MDI (9)                         --   8453                                  200    15    12 11300            DIPIP (3)                  H-MDI (4)                         1.33 8383                                  500    6    13 21200            DIPIP (6)                  IPDI (7)                         1.07 5210                                  300    5    14 21200            DIPIP (6)                  H-MDI (7)                         1.15 4382                                  375    10    15 36300            DIPIP (9)                  H-MDI (10)                         1.21 3002                                  520    10    __________________________________________________________________________     Chain Extender     DIPIP = 1,3di(4-piperidyl)propane     Diisocyanates     HMDI = Methylene 4,4' dicyclohexane isocyanate (hydrogenated  MDI)     IPDI = Isophorone diisocyanate

EXAMPLE 16

Preparation of Silicone Diamine by the Prior Art Procedure

To 10 g of octamethylcyclotetrasiloxane (D₄), previously purged for 20minutes with argon, was added 0.08 g of tetramethyl ammonium hydroxidepentahydrate. After stirring at 80° C. under argon for 30 minutes, themixture became very viscous indicating that conversion to tetramethylammonium siloxanolate (the actual catalyst) had occurred. A solution of2.5 g bis (aminopropyl)tetramethyl disiloxane endblocker (0.01 mole) in105 g of D₄ was added all at once to produce a clear solution which wasstirred at 80° C. to 85° C. under argon to provide an assumed 85% yieldof polymer having a theoretical molecular weight of 10,000.

After heating the clear solution for 24 hours, it was determined by VPCthat a substantial amount of endblocker had not been incorporated intothe polymer After 48 hours, although VPC indicated that someunincorporated endblocker was still present, the reaction was terminatedby heating to 150° C. for 30 minutes. The resultant clear, colorless oilwas stripped under aspirator vacuum at 120° to 130° C. for one hour toremove all volatiles, leaving 103 g (87% yield) of product.

Titration of the product with 0.1N hydrochloric acid revealed an aminocontent of 0.166 meq/g or a calculated molecular weight of 12,043assuming the product is completely difunctional.

EXAMPLE 16A

Preparation of Silicone Diamine by the Prior Art Procedure

The siloxanolate catalyst was prepared as described above from 30 g D₄and 0.20 g of Me₄ NOH•5H₂ O. To this catalyst was added a solution of9.92 g (H2NCH₂ CH₂ CH₂ Si)₂ --O endblocker (0.04 mole) in 200 g D₄. Themixture was stirred and heated at 85° C. under argon, and the course ofthe reaction was followed by VPC After 18 hrs, no endblocker remained inthe mixture, and the reaction was terminated by heating at 150° C. for30 minutes. Residual cyclics were distilled at 130°-150° C. at 0.1 mmHg, to provide the product as a clear, colorless oil which was cooled toroom temperature. The yield was 198 g (83% yield). Titration of theproduct with 0.1N HCl gave a molecular weight of 5412. The theoreticalmolecular weight was 5000.

EXAMPLE 17

Preparation of Silicone Polyurea Elastomer Using Prior Art SiliconeDiamine

A 100 ml one-neck round bottom flask was charged with 10.51 g of the12,043 molecular weight silicone diamine of Example 16 and dissolved in50 ml of dichloromethane. A solution of 0.91 g H-MDI in 10 mldichloromethane was added all at once with stirring. The resulting clearsolution was treated dropwise with stirring with a solution of 0.55 g1,3-bis(4-piperidyl)propane (DIPIP) in 5 ml of dichloromethane. Towardthe end of the addition, the solution became viscous but remained clear.After 1/2 hour, the viscous solution was cast on a glass plate, leavingan elastomeric film, upon solvent evaporation, of a polyurea with asilicone diamine/DIPIP/H-MDI molar ratio of 1:3:4.

EXAMPLE 17A

Preparation of Silicone Polyurea Elastomer Using Prior Art SiliconeDiamine

Following the procedure described in Example 17 above, a siliconepolyurea elastomer was prepared from 16.03 g of the 5412 molecularweight silicone diamine of Example 16A, 0.62 g DIPIP, and 1.55 g H-MDIin dichloromethane solution. After casting on a glass plate, a clearsilicone polyurea elastomer was obtained having the molar ratio ofsilicone diamine/DIPIP/H-MDI of 1:1:2.

EXAMPLE 18

Comparison of Elastomeric Properties of Silicone Polyureas Prepared with"Prior Art" Silicone Diamines and Present Invention Diamines

The tensile strength, inherent viscosity, elongation at break, andpermanent set of the silicone polyureas of Examples 17 and 17A werecompared to the properties of analogous silicone polyureas derived fromsilicone diamines of similar molecular weight prepared by the method ofthe present invention. Results are shown in Table II. Included in thisTable II are results obtained from the extraction of these films withboiling cyclohexane (Extractable Oil). Significant amounts of freesilicone oil were obtained from films prepared using the "Prior Art"diamines when compared to the films prepared using diamines of theinvention. As the molecular weight of the diamine was increased, therelative level of impurities also increased, resulting in progressivelyinferior physical properties when compared to the polyureas of thepresent invention.

                  TABLE II    ______________________________________                                  Elon-                                  gation          Mol.                    at    Perm.    Ex.   Wt. of   Inherent Tensile                                  Break Set   Extract.    No.   Diamine  Viscosity                            (kPa) (%)   (%)   Oil (%)    ______________________________________    17A   5,400    .67      6916  555   37    3.0    Prior    Art    17    12,000   .51      3312  290   3     6.0    Prior    Art    Ex. 3 5,300    .70      8034  550   35    1.0    The    invent.    Ex. 12          11,300   1.33     8383  500   6     1.2    The    invent.    ______________________________________

EXAMPLE 19

A Silicone-Polyether Polyurea Copolymer

A mixture of 8.2 g of a silicone diamine of 8215 molecular weight, 7.3 gof 7,300 molecular weight polytetramethylene oxide diamine, and 0.67 gof DIPIP was dissolved in a solvent system of 90 ml isopropyl alcoholand 50 ml of dichloromethane. With stirring at room temperature, 1.11 gof isophorone diisocyanate was added dropwise. Toward the end of theaddition, the solution became quite viscous but remained clear and didnot gel. A film was cast from the viscous solution, dried and theresulting crystal clear silicone-polyether elastomer had a tensilestrength of 19,458 kPa, 650% elongation and 6% permanent set.

EXAMPLE 20

Silicone-Polyester Polyurethane Polyurea Copolymer Elastomers

A one liter, three-necked round bottom flask was charged with 19.2 g of2000 molecular weight polycaprolactone diol ("Tone"-0240 from UnionCarbide) and 100 ml toluene. The solution was heated to boiling and asmall quantity of solvent was allowed to distill from the flask toazeotropically dry the contents. Isophorone diisocyanate (9.92 grams)was added, followed by three drops of the catalyst dibutyl tindilaurate. After an initial vigorous reaction, the clear solution washeated under reflux for 1/2 hour. The reaction was diluted to 300 mlwith toluene and a solution of 24 g of a 10,350 molecular weightsilicone diamine in 50 ml of toluene was added fairly rapidly withstirring. The resulting clear, colorless solution was treated rapidlywhile stirring with a solution of 6.88 g of 1,3-bis (4-piperidyl)propane in 100 ml of isopropyl alcohol. The reaction became quiteviscous but remained clear. After an additional hour, the solution wascast in a tray and the solvent allowed to evaporate. The resultingelastomer, a silicone-polyester polyurethane polyurea, contained 40%silicone and was clear, strong and highly elastic.

EXAMPLES 21-24

Preparation of Pressure-Sensitive Adhesive Using Polysiloxane PolyureaBlock Copolymer

A 200 ml round bottom flask was charged with 23.23 g of freshly preparedsilicone diamine of 21,213 molecular weight and 35.3 g of toluene. Thesolution was stirred at room temperature and 0.29 of H-MDI was addedfollowed by another 28 g toluene. After 20 minutes, the solution hadbecome very viscous. The pressure-sensitive adhesive was produced byadding 39.2 g of a 60% solution in xylene of an MQ silicone resincomposition available from General Electric Company as SR-545. The finalsolids content was adjusted to 35% by the further addition of 10.3 g oftoluene. The resulting pressure-sensitive adhesive solution had asilicone polyurea gum to MQ resin weight ratio of 1:1.

By a similar procedure, a number of other silicone polyureapressure-sensitive adhesives were prepared by blending the polyureaobtained from the reaction of silicone diamines of various molecularweights with equimolar amounts of diisocyanates with an equal weight ofMQ silicate resin. These were coated onto polyester film at a 25 to 33μm thickness to provide pressure-sensitive adhesive flexible sheetmaterials.

The performance of these examples was evaluated by two standard testmethods as described by the American Society of Testing and Materials(ASTM) of Philadelphia, Pa. and the Pressure Sensitive Tape Council(PSTC) of Glenview, Ill. These are Procedures No. 1 (peel adhesion) andNo. 7 (shear strength).

Peel Adhesion ASTM P3330-78 PSTC-1 (11/75)

Peel adhesion is the force required to remove a coated flexible sheetmaterial from a test panel measured at a specific angle and rate ofremoval. In the examples this force is expressed in Newtons per 100 mm(N/100 mm) width of coated sheet. The procedure follows:

1. A 12.5 mm width of the coated sheet is applied to the horizontalsurface of a clean glass test plate with at least 12.7 lineal cm in firmcontact. A hard rubber roller is used to apply the strip.

2. The free end of the coated strip is doubled back nearly touchingitself, so the angle of removal will be 180° . The free end is attachedto the adhesion tester scale.

3. The glass test plate is clamped in the jaws of the tensile testingmachine which is capable of moving the plate away from the scale at aconstant rate of 2.3 meters per minute.

4. The scale reading in Newtons is recorded as the tape is peeled fromthe glass surface. The data is recorded as the average value of therange of numbers observed during the test.

Shear Holding Strength (Reference: ASTM: D3654-78; PSTC-7)

The shear strength is a measure of the cohesiveness or internal strengthof an adhesive. It is based upon the amount of force required to pull anadhesive strip from a standard flat surface in a direction parallel tothe surface to which it has been affixed with a definite pressure it ismeasured in terms of time (in minutes) required to pull a standard areaof adhesive coated sheet material from a stainless steel test panelunder stress of a constant, standard load.

The tests were conducted on adhesive coated strips applied to astainless steel panel such that a 12.5 mm portion of each strip was infirm contact with the panel with one end portion of the tape being free.The panel with coated strip attached was held in a rack such that thepanel forms an angle of 178° with the extended tape free end which isthen tensioned by application of a force of one kilogram applied as ahanging weight from the free end of the coated strip. The 2° less than180° is used to negate any peel forces thus insuring that only the shearforces are measured in an attempt to more accurately determine theholding power of the tape being tested. The time elapsed for each tapeexample to separate from the test panel is recorded as the shearstrength.

For the examples of pressure-sensitive adhesives prepared from siliconepolyureas without chain extenders, the peel adhesion and shear resultsare listed in Table III.

                  TABLE III    ______________________________________    Silicone Polyurea Pressure-Sensitive Adhesive     (1:1 Silicone Diamine/H-MDI) Gum: MQ Resin = 1:1!                  PSA    Ex.    Silicone     Adhesion   Shear (23° C.)    No.    Diamine MW   (N/100 mm) (Minutes)    ______________________________________    22     10,300       12         10000+    21     21,200       43         10000+    23     36,380       61         234    24     53,500       52         382    ______________________________________

EXAMPLES 25-29

Preparation of Pressure-Sensitive Adhesives Using Polysiloxane PolyureaBlock Copolymers With Chain Extenders

A solution of 17.55 g of 34,000 molecular weight silicone diamine(0.0585 meq/g) in 100 ml of methylene chloride was rapidly added at roomtemperature with stirring to a solution of 0.54 g of methylene bis4,4'dicyclohexyl!isocyanate (H-MDI) in 50 ml of methylene chloride. Asolution of 0.12 g of 1,3-bis(4-piperidyl) propane (DIPIP) in 25 ml ofmethylene chloride was slowly added dropwise resulting in asilicone-polyurea solution which became viscous but did not gel uponcompletion of the second addition. To prepare the pressure-sensitiveadhesive, there was added 30.7 of a 60% xylene solution of MQ silicateresin (SR-545) producing 1:1 silicone block copolymer to tackifierweight ratio. The solution containing this adhesive was cast onpolyester to produce a 33 txm adhesive film which was tested accordingto Pressure Sensitive Tape Council (PSTC) Procedures No. 1 (peeladhesion) and No. 7 (shear strength). The results showed 50N/100 mm ofpeel adhesion to glass and 10,000 plus minutes of shear holding time.This is compared to a number of other pressure-sensitive adhesivecompositions of the invention using silicone diamines having differingmolecular weight as shown in Table IV.

                  TABLE IV    ______________________________________    Silicone Polyurea Pressure-Sensitive Adhesive    (With Chain Extender)    Silicone-Polyurea Gum                         PSA                   DIPIP                   Shear          Silicone Chain           Peel    Holding    Ex.   Diamine  Extender H-MDI  Adhesion                                           23° C.    No.   (MW)     (Moles)  (Moles)                                   N/100 mm                                           Minutes    ______________________________________    26    21,000   4        5      10      10,000+    27    21,000   3        4      28      10,000+    28    19,000   2        3      31      --    25    34,000   3        4      50      --    29    55,000   2        3      76 (split)                                           --    ______________________________________

EXAMPLE 30

Preparation of Copolymer to be used as Release Agent

    ______________________________________    Composition:    ______________________________________    PDMS (MW-5560)      25 parts by weight    PCL (MW-1250)       35 parts by weight    DIPIP/IPDI          40 parts by weight    ______________________________________

Procedure:

Polycaprolactone diol (PCL) (35 g) in toluene was refluxed undernitrogen for 30 minutes with the entire charge of IPDI (24.06 g) in thepresence of a catalytic amount (3 drops) of dibutyl tin dilaurate. Afterreflux, heat was removed and toluene was added to dilute the entire massto 500 ml. After cooling to room temperature, the PDMS diamine (25.0 g)along with 100 ml toluene was added and stirred for 15 minutes.

Then DIPIP (15.94 g), dissolved in 100 ml isopropanol, was added slowlyover a period of 2-3 minutes and stirred for 30 minutes. An increase inviscosity was observed within 5 minutes. The entire solution remainedclear and colorless throughout the procedure. A final dilution withtoluene brought the solids level to approximately 10% in the solventblend of 90:10 ratio of toluene:isopropanol. A 1.5 rail urethanesaturated smooth crepe paper backing was primed with a chloroprenelatex, Neoprene TM (N-115) made by DuPont, in one trip. In a secondtrip, the LAB was applied from a metering roll to the opposite side ofthe backing using a 50% solid solution in toluene/isopropanol. Finally,in a third trip, to the primer side was applied a latex adhesive (45%natural rubber/57% Piccolyte TM S-65, a poly beta-pinene tackifyingresin with a ring and ball softening point of 65° C. made by HerculesCo.), of coating weight of 4.4 mg/cm².

EXAMPLE 31

    ______________________________________    Composition:    ______________________________________    polydimethyl-diphenyl                      25% (contains 10 mole %    siloxane (PDMDPS) diphenylsiloxane)    (MW 2680)    PCL (MW 1250)     35%    DIPIP/IPDI        40%    ______________________________________

This was prepared and coated similar to procedure used in Example 30.

EXAMPLE 32

    ______________________________________    Composition:    ______________________________________    PDMS (MW 5590)          10%    PCL (MW 1240)           60%    DIPIP/IPDI              15%    DAS/IPDI                15%    ______________________________________

This was coated similar to the procedure used in Example 30.

EXAMPLE 33

    ______________________________________    Composition:    ______________________________________    PDMS (MW 4900)          23%    PCL (MW 1250)           42%    DIPIP/IPDI              35%    ______________________________________

This was coated similar to the procedure used in Example 30. The testresults from the above examples are tabulated in Table V.

EXAMPLE 34

    ______________________________________    Composition:    ______________________________________    PDMS (MW 4900)          20%    PCL (MW 1250)           20%    DIPIP/IPDI              60%    ______________________________________

This was coated similar to the procedure of Example 30.

TESTING

The performance of Examples 30-34 was evaluated by the standard testmethod for peel adhesion as described supra and the unwind testdescribed below.

UNWIND TEST

Testing was accomplished using an Instron-type testing at 90° angle and90 in/min separation. Data is presented in ounces per inch.

                  TABLE V    ______________________________________    UNWIND    UNWIND    Ex.   3 WEEKS RT   65° C./16 HRS                                    90%-50% RH    ______________________________________    30    17           21           21    31    26           21           --    32    23           12           24    33    22           12           20    34    11           17           n/a    ______________________________________    PEEL ADHESION TEST    PEEL ADHESION TEST    Ex.   3 WEEKS RT   65° C./16 HRS                                    90%-50% RH    ______________________________________    30    53           52           51    31    51           51           --    32    50           50           50    33    51           49           52    34    50           50           --    ______________________________________     RT = 22° C./50% Relative Humidity  65° C./16 Hrs. was     followed by 24 Hrs. at 22° C./50% Relative Humidity  90%-50%: Tape     was aged at 32° C./90% Relative Humidity for 2 weeks followed by 1     week at 22° C./50% Relative Humidity.

All examples were coated from 5% solutions on ULTRA backing using ametering roll.

EXAMPLE 35

Preparation of cesium 3-aminopropyldimethyl silanolate

A 250 ml 1-neck round bottom flask equipped with magnetic stirrer and acondenser fitted with a Dean-Stark water separator was charged with 7.9g bis(3-aminopropyl)tetramethyldisiloxane (available from Silar ChemicalCo.), 20 g of cesium hydroxide as a 50% aqueous solution (available fromAldrich Chemical Co.), and 100 ml toluene. The mixture was heated underreflux for 16 hours with azeotropic removal of water. The resultingclear, colorless solution was cooled to room temperature, the productprecipitated by addition of hexane until hazy while cooling in an icebath, and decanting the supernatant liquid from the solid. Thisprecipitate was re-dissolved in 20 ml of hot toluene, cooled to ambienttemperature, and 60 ml hexane slowly added with stirring; the resultingsolid was isolated by filtration under nitrogen and dried in vacuo. 13.4g of a white crystalline solid (76% yield) was obtained. The ¹⁴ C and ¹H nmr spectra and elemental analysis confirmed the product to be thedesired pure, anhydrous cesium 3-aminopropyl dimethylsilanolate.

EXAMPLE 36

Preparation of rubidium 3-aminopropyl dimethylsilanolate

In a similar procedure to that described for Example 35 above, rubidium3-aminopropyl dimethylsilanolate was prepared from 5.7 gbis(3-aminopropyl)tetramethyl disiloxane and 11.3 g of 50% aqueousrubidium hydroxide in 50 ml toluene. In this case, the productprecipitated immediately upon cooling of the toluene reaction;filtration and drying gave the desired rubidium silanolate.

EXAMPLE 37

Preparation of organopolysiloxane diamine using cesium silanolate ascatalyst

A mixture of 9.94 g bis(3-aminopropyl)tetramethyl disiloxane and 470.59g octamethylcyclotetrasiloxane, which had been previously purged bybubbling dry argon gas through it for 20 min, was stirred and heated to150° C.; 0.319 g cesium 3-aminopropyl dimethyl silanolate of Example 35(25 ppm) was added, and heating continued. In about 20 minutes, theviscosity had increased significantly, and after 3 hours, analysis of asample by gas chromatography showed complete disappearance of thestarting aminopropyl disiloxane and the expected equilibriumdistribution of cyclic siloxanes. The solution was cooled to ˜60 to 80°C., 0.03 g acetic acid added, the mixture stirred for 0.5 hour, and thenheated to 150° C. under high vacuum to remove residual cyclic siloxanes.After 4 to 6 hours, no more volatiles were collected. The mixture wasthen cooled to room temperature and filtered to separate theprecipitated cesium acetate. The resulting clear, colorless oil amountedto an 411.12 g (87%) % yield. A sample dissolved in 50%tetrahydrofuran/isopropyl alcohol was titrated with 0.1N HCl to abromphenol blue end point had a molecular weight of 10,400 (10,000theoretical).

EXAMPLE 38

Preparation of organopolysiloxane diamine using cesium hydroxide.

A solution of 7.48 g of bis(3-aminopropyl)tetramethyl disiloxane and352.9 g octamethylcyclotetrasiloxane was purged with argon for 20 minand then heated to 150° C.; 0.06 g (100 ppm) of 50% aqueous cesiumhydroxide was added and heating continued for 6 hours until theaminopropyl disiloxane had been consumed. The reaction was cooled to 70°C., neutralized with excess triethylamine and acetic acid, and heatedunder high vacuum to remove cyclic siloxanes over a period of at least 5hours. After cooling to ambient temperature and filtering to removecesium acetate, the isolated product (3 15 g) titrated to a molecularweight of 10,491 (theoretical 10,000 molecular weight).

EXAMPLE 39

Preparation of a organopolysiloxane diamine from a lower molecularweight organopolysiloxane diamine

A 1000 ml 3-neck round bottom flask equipped with mechanical stirrer,nitrogen inlet, and vacuum adapter was charged with 30 g of anorganopolysiloxane diamine having a titrated molecular weight of 5,376made according to the method of Example 37 and 300 goctamethylcyclotetrasiloxane. The mixture was stirred and heated from100° C. to 150° C. and 0.06 g of cesium silanolate catalyst of Example35 was added. The viscosity of the reaction rose rapidly and, after 30min, gas chromatography of a sample showed the equilibrium distributionof volatile cyclic siloxanes. The reaction was cooled to 70° C., and 0.1g or triethylamine and 0.06 g acetic acid were added. After stirring for30 min, a ²⁹ Si nmr analysis of silanol content was performed on thisintermediate. The intermediate was then heated to 150° C. under highvacuum of 30 mm for 10 minutes to distill volatile cyclic siloxanes. Thevacuum was released and the mixture was heated to 150° C. After coolingto room temperature and filtering to remove cesium acetate, theorganopolysiloxane diamine having a titrated molecular weight of 50,329(50,000 theoretical) was isolated as a clear, colorless oil.

EXAMPLE 40

Preparation of a organopolysiloxane diamine from a lower molecularweight organopolysiloxane diamine

A organopolysiloxane diamine having a theoretical molecular weight of50,000 was prepared according to the method of Example 39 using 53.76 gof a 5000 molecular weight organopolysiloxane diamine made according tothe method of Example 37, 534.48 g octamethylcyclotetrasiloxane, and0.0125 g cesium silanolate catalyst. After cooling, 0.004 grams aceticacid were added and, after the volatile cyclic siloxanes were distilledand the cesium acetate filtered, a product having a titrated molecularweight of 49,844 was obtained.

EXAMPLE 41

Preparation of a organopolysiloxane diamine from a lower molecularweight organopolysiloxane diamine

A organopolysiloxane diamine having a theoretical molecular weight of75,000 was prepared according to the method of Example 39 using 28.67 gof a 5000 molecular weight organopolysiloxane diamine made according tothe method of Example 37, 441.92 g octamethylcyclotetrasiloxane, and0.02 g cesium silanolate catalyst. After cooling, 0.009 grams aceticacid were added and, after the volatile cyclic siloxanes were distilledand the cesium acetate filtered, a product having a molecular weight of67,982 (as measured by ²⁹ Si nmr analysis) was obtained.

EXAMPLE 42

Preparation of organopolysiloxane diamine using cesium hydroxide.

A solution of 0.992 g of bis(3-aminopropyl)tetramethyl disiloxane and352 g octamethylcyclotetrasiloxane was purged with carbon dioxide for 15min and then heated to 150° C.; 0.06 g (100 ppm) of 50% aqueous cesiumhydroxide was added and the mixture was heated to 150° C. for 24 hoursuntil the aminopropyl disiloxane had been consumed. The reaction wascooled to 70° C., neutralized with 0.2 g excess triethylamine and 0.06 gacetic acid, and the very thick and bubbly mixture was heated slowly to150° C. under high vacuum to remove cyclic siloxanes over a period of atleast 5 hours. After all of the mixed cyclic siloxanes were distilledand collected, the product was cooled to ambient temperature andfiltered to remove cesium acetate. 318 g of the organopolysiloxanediamine product was obtained. The titrated molecular weight of theproduct was 75,634 (theoretical 75,000).

EXAMPLE 43

Preparation of a organopolysiloxane diamine from a lower molecularweight organopolysiloxane diamine

A organopolysiloxane diamine having a theoretical molecular weight of100,000 was prepared according to the method of Example 39, except thatthe reaction was run in a 94.7 liter (25 gal) stainless steel reactor,starting from 45 kg (6.2 lbs.) of a organopolysiloxane diamine having amolecular weight of 5000 made according to the method of Example 2,1234.8 kg (170 lbs.) mixed dimethyl substituted cyclic siloxanes(available as "DMC Dimethyl Cyclics" from Shin-Etsu Chemical Co.), and16.0 g cesium hydroxide solution (for a targeted molecular weight of100,000). After 1 hr at 150° C., the reaction had reached completeequilibrium and had become very viscous. The crude product was cooled to80° C., terminated with 20.0 g triethylamine and 10.0 g acetic acid, andthen re-heated to 150° C. under high vacuum to distill volatile cyclicsiloxanes. This removal of cyclics was facilitated by allowing nitrogento bubble up from the reactor bottom during the distillation. After 7hours, no more cyclics were collected, and the contents were cooled toambient temperature to provide 871.7 kg (120 lbs., 68% yield) of thedesired organopolysiloxane diamine having a titrated molecular weight of100,800.

EXAMPLE 44

Preparation of a organopolysiloxane diamine from a lower molecularweight organopolysiloxane diamine

A organopolysiloxane diamine having a theoretical molecular weight of20,000 was prepared according to the method of Example 43. 987 g of a5000 molecular weight organopolysiloxane diamine, 1256.7 kg (173 lbs.)mixed dimethyl substituted cyclic siloxanes (available as "DMC DimethylCyclics" from Shin-Etsu Chemical Co.) and 16 g cesium hydroxide weremixed under reaction conditions. After cooling, 20 g triethylamine and16 grams acetic acid were added and a ²⁹ Si nmr analysis of silanolcontent was performed on this intermediate. Following this measurement,the volatile cyclic siloxanes were distilled and the cesium acetatefiltered, a product having a titrated molecular weight of 20,000 wasobtained.

TESTING FOR SILANOL IMPURITIES

Comparison of purity of organopolysiloxane diamines prepared usingdifferent catalysts and methods

The organopolysiloxane diamine products described in Examples 12, 37-44were examined by ²⁹ Si nmr spectroscopy and recorded in Table VI. Forcomparative purposes, ²⁹ Si nmr analysis of organopolysiloxane diaminesmade by the prior art method from Example 16 have also been provided.This method was used to determine the average molecular weight, amineand silanol endgroup distribution ratios, and the relative weightpercent silanol content for these examples. The organopolysiloxanediamine samples were dissolved in chloroform-d₁, a relaxation agent(chromium acetonyl acetonate) added, and the spectra were acquired usinga Varian Unity 300 NMR spectrometer operating at 59.59 MHz. Relativeintegrated area ratios of the amine endgroups (--NH₂) silicon peak,silanol endgroups (--SiOH) silicon peak, and the poly(dimethylsiloxane)silicon peak were used to calculate the values.

                  TABLE VI    ______________________________________                                     %      %                                     NH.sub.2                                            --SiOH                              Wt. % S                                     End-   End-    Ex.    Catalyst  M.sub.W  iOH    groups groups    ______________________________________    16     NMe.sub.4 OH                     12,043   0.019  93.8   6.2    (Comp.)    12     NMe.sub.4 OSi                     11,300   0.010  97.4   2.6    37     CsOSi     10,400   0.005  98.5   1.5    38     CsOH      10,491   0.006  98.2   1.8    39.sup.1           CsOH      50,329   0.014  81.5   18.5    39.sup.2           CsOH      50,329   0.005  92.3   7.7    40     CsOSi     49,844   0      100    0    41     CsOSi     67,982   0      100    0    42     CsOH      75,634   0.002  95.8   4.2    43     CsOH      100,800  0      100    0    44.sup.1           CsOH      20,000   0.017  91.2   8.8    44.sup.2           CsOH      20,000   0.004  97.9   2.1    ______________________________________     .sup.1 denotes purity of organopolysiloxane diamine prior to treatment     with cesium acetate salt     .sup.2 denotes purity of organopolysiloxane diamine following treatment     with cesium acetate salt     "CsOSi" denotes cesium 3aminopropyldimethyl silanolate     "NMe.sub.4 OSi" denotes tertamethylammonium 3aminopropyl silanolate

Table VI clearly illustrates that the methods of the present inventioncan be used to prepare novel organopolysiloxane diamines having a broadrange of molecular weights and very low levels (0.010 wt. % and less) ofsilanol endgroups, particularly when compared to those materials made bypreviously known methods (Example 16). As repeatedly stressed throughoutthe present application, highly difunctional, high molecular weightorganopolysiloxane diamines are essential in preparing a variety ofelastomeric compositions and, prior to the present invention, none ofthe known methods for producing such compounds could yield a diamine ofsufficient purity to result in the superior elastomeric materialsdescribed herein.

While this invention has been described in connection with specificembodiments, it should be understood that it is capable of furthermodification. The claims herein are intended to cover those variationswhich one skilled in the art would recognize as the chemical equivalentof what has been described here.

What is claimed is:
 1. A method of making an organopolysiloxane diaminehaving a number average molecular weight greater than 2000 and havingless than or equal to about 0.010 weight % silanol impurities,comprising the steps of:(a) forming a mixture consisting essentiallyof(i) an amine functional endblocker represented by the formula IX##STR11## wherein; Y is selected from the group consisting of alkyleneradicals comprising about 1 to about 10 carbon atoms, aralkyl radicals,and aryl radicals; D is selected from the group consisting of hydrogen,an alkyl radical of about 1 to about 10 carbon atoms, and phenyl; R isat least 50% methyl with a balance of the 100% of all R radicals beingselected from the group consisting of a monovalent alkyl radical having2 to 12 carbon atoms, substituted alkyl radical having from 1 to 12carbon atoms, a vinyl radical, a phenyl radical, and a substitutedphenyl radical; and x represents an integer of about 1 to about 150;and(ii) sufficient cyclic siloxane to obtain said organopolysiloxanediamine having a number average molecular weight greater than about2000; (b) removing any volatile contaminants from the mixture; (c)heating the mixture to about 100° to about 160° C. under an inertatmosphere; (d) adding a catalytic amount of a compound selected fromthe group consisting of cesium hydroxide, rubidium hydroxide, cesiumsilanolates, rubidium silanolates, cesium polysiloxanolates, rubidiumpolysiloxanolates, and mixtures thereof, to the mixture which has beenheated; (e) continuing the reaction until substantially all of saidamine functional endblocker is consumed; (f) terminating the reaction bythe addition of a volatile organic acid to form a mixture of anorganopolysiloxane diamine having greater than about 0.010 weight %silanol impurities and one or more of the following: a cesium salt ofthe organic acid, a rubidium salt of the organic acid, both a cesiumsalt of the organic acid and a rubidium salt of the organic acid;wherein a molar excess of organic acid is added in relation to thecompound of element (d); (g) condensing under reaction conditions asufficient amount of said silanol impurities to form anorganopolysiloxane diamine having less than or equal to about 0.010weight % of silanol impurities; and (h) optionally removing said salt.2. The method of claim 1 wherein the endblocker has greater than about0.010 weight % silanol impurities.
 3. The method of claim 1 wherein theendblocker has less than or equal to about 0.010 weight % of silanolimpurities.
 4. The method of claim 1 wherein said organopolysiloxanediamine having a number average molecular weight greater than about5000.
 5. The method of claim 1 wherein x represents an integer of about1 to about 70 and Y is selected from the group consisting of --CH₂ CH₂CH₂ -- and --CH₂ CH₂ CH₂ CH₂ --.
 6. The method of claim 1 wherein about0.005 to about 0.3 weight percent of the compound of element (a)(iii) isused based upon the total weight of the endblocker and the cyclicsiloxane, and wherein said compound is selected from the groupconsisting of cesium silanolates, rubidium silanolates, and mixturesthereof.
 7. The method of claim 1 wherein about 0.005 to about 1 weightpercent of the compound of element (a)(iii) is used based upon the totalweight of the endblocker and cyclic siloxane, and wherein said compoundis selected from the group consisting of cesium hydroxide, rubidiumhydroxide, and mixtures thereof.
 8. The method of claim 1 wherein saidvolatile organic acid is selected from the group consisting of aceticacid, trimethylacetic acid, trichloroacetic acid, trifluoroacetic acid,benzoic acid, and mixtures thereof.
 9. The method of claim 1 whereinsaid reaction conditions of element (a) comprise a reaction temperatureof about 150° C. to about 160° C. and a reaction time of about 0.5 toabout 2 hours.
 10. The method of claim 1 wherein said reactionconditions of element (d) comprise a reaction temperature of about 130°C. to about 160° C. and a reaction time of about 4 to about 8 hours andwherein the reaction is conducted under vacuum.
 11. A method of makingan organopolysiloxane diamine having a number average molecular weightof at least 5000 and being prepared by the steps of(1) combining underreaction conditions:(a) amine functional endblocker of the generalformula wherein; ##STR12## Y is selected from the group consisting ofalkylene radicals of about 1 to about 10 carbon atoms, aralkyl, and arylradicals; D is selected from the group consisting of hydrogen, an alkylradical of 1 to 10 carbon atoms, and phenyl; and R is each independentlyselected from the group consisting of a monovalent alkyl radical havingfrom 1 to 12 carbon atoms, a substituted alkyl radical having from 1 to12 carbon atoms, a phenyl radical, and a substituted phenyl radical; (b)sufficient cyclic siloxane to react with said amine functionalendblocker to form an intermediate organopolysiloxane diamine having anumber average molecular weight less than about 2,000 and generalformula ##STR13## where: Y and D are as defined above; R is at least 50%methyl with the balance of the 100% of all R radicals being selectedfrom the group consisting of a monovalent alkyl radical having from 2 to12 carbon atoms, a substituted alkyl radical having from 1 to 12 carbonatoms, a vinyl radical, a phenyl radical and a substituted phenylradical; and x is a number in the range of about 4 to about 40; and (c)a catalytic amount of a compound characterized by having a molecularstructure represented by the formula: ##STR14## where; Y and D are asdefined above; R is each independently selected from the groupconsisting of a monovalent alkyl radical having from 1 to 12 carbonatoms, a substituted alkyl radical having from 2 to 12 carbon atoms, aphenyl radical, and a substituted phenyl radical; and M⁺ is selectedfrom the cations K⁺, Na⁺ and N(CH₃)₄ ⁺ ; (2) continuing the reactionuntil substantially all of said amine functional endblocker is consumed;and (3) adding additional cyclic siloxane until said organopolysiloxanediamine having a number average molecular weight of at least 5000 isformed.
 12. A method of making an organopolysiloxane diamine having anumber average molecular weight of at least about 2000 and having lessthan or equal to about 0.010 weight % silanol impurities, and beingprepared by the steps of(1) combining under reaction conditions:(a)amine functional endblocker of the general formula ##STR15## where; Y isselected from the group consisting of an alkylene radical of 1 to 10carbon atoms, aralkyl, and aryl radicals; D is selected from the groupconsisting of hydrogen, an alkyl radical of 1 to 10 carbon atoms, andphenyl; and R is each independently selected from the group consistingof a monovalent alkyl radical having from 1 to 12 carbon atoms, asubstituted alkyl radical having from 1 to 12 carbon atoms, a phenylradical, and a substituted phenyl radical; (b) sufficient cyclicsiloxane to react with said amine functional endblocker to form anintermediate organopolysiloxane diamine having a number averagemolecular weight less than about 2000 and general formula ##STR16##where: Y and D are as defined above; R is at least 50% methyl with thebalance of the 100% of all R radicals being selected from the groupconsisting of a monovalent alkyl radical having from 2 to 12 carbonatoms, a substituted alkyl radical having from 1 to 12 carbon atoms, avinyl radical, a phenyl radical and a substituted phenyl radical; and xis a number in the range of about 4 to about 40; and (c) a catalyticamount of a compound characterized by having a molecular structurerepresented by the formula: ##STR17## where: Y and D are as definedabove; R is each independently selected from the group consisting of amonovalent alkyl radical having from 1 to 12 carbon atoms, a substitutedalkyl radical having from 2 to 12 carbon atoms, a phenyl radical, and asubstituted phenyl radical; and Q⁺ is selected from the cations Cs⁺ andRb⁺ ; (2) continuing the reaction until substantially all of said aminefunctional endblocker is consumed; (3) adding additional cyclic siloxanein an amount required to obtain the organopolysiloxane diamine of thedesired molecular weight; (4) terminating the reaction by addition of avolatile organic acid to form the organopolysiloxane diamine of at leastabout 2000 number average molecular weight having less than or equal toabout 0.010 weight percent silanol impurities; and (5) removing anyresidual cyclic siloxanes and volatile impurities.
 13. The method ofclaim 12 wherein said reaction conditions comprise a reactiontemperature of about 150° to about 160° C. and a reaction time of about0.5 to about 2 hours.
 14. The method of claim 12 wherein the compound ofelement (1)(c) is used at less than about 0.025 weight percent basedupon the total weight of the organopolysiloxane diamine.
 15. The methodof claim 12 wherein the compound of element (1)(c) is used at about0.0025 to about 0.01 weight percent based upon the total weight of theorganopolysiloxane diamine.
 16. The method of claim 12 wherein theorganopolysiloxane diamine has a number average molecular weight greaterthan about 5000.